THE Prime Minister's chance disclosure that he is not contemplating a third term in office has rattled his party, unused to seeing its internal speculation about succession made suddenly public. The party's brand managers face the prospect of taking a familiar product off the shelf - possibly before its sell-by date has been reached - and having to construct a marketing campaign for another. Thus far has British politics become personal.

Besides annoying his party's grandees, David Cameron's remark did several things. First, it assumed that he would have a second term in office, not a view shared by his political opponents. A similar degree of presumption was blamed for Neil Kinnock's defeat in 1992. Second, it excited the pundits to to the extent that The Times front page announced "Cameron fires start gun on Tory leadership race". Third, it reminded voters that Mr Cameron is a human being, able to contemplate life after holding the highest office. Predecessors in the post have had either to be voted out or carried out. No tear-stained face peering from the car window for him. But, fourth, it has given rise to the absurd notion that Mr Cameron's heart is no longer in the job. If someone can talk relatively openly about giving up, what does that say to the voters about his commitment to the office that he holds?

It says nothing that they could not have worked out for themselves, of course. The fixing of a five-year period between elections, one of Mr Cameron's first acts in 2000, made it all the more improbable that a politician could progress easily into a third term. Also, the demands of the job, and the keen scrutiny under which a Prime Minister now lives, are bound to take their toll. If the politician cannot see that, then the family man should. Assuming the media calms down - and five years is a long time to be talking about runners and riders - Mr Cameron's move will be seen as a sign of sound common sense. And by stating it publicly, however intentional this was, he has ensured that he must stick to it. The one caveat relates to public service. Mr Cameron must beware of giving the impression that his commitment to the public good is time-limited. Any suggestion that he is looking forward to a period of privileged wealth creation after leaving Downing Street would undermine any vestiges of belief that the Conservatives are concerned with equality of opportunity.

The combative nature of party politics, where a lost policy or a lost appointment for one side is a gain for the other, makes it hard for people to contemplate the voluntary relinquishing of power, even at this remove. Christians, however, view this affair from a different perspective. The Gospels are, among many other things, a study in the nature of power, and what God thinks of it. The regal period of Christ's ministry lasted a few days at most. Although he signalled to his disciples that his period of office was extremely time-limited, they were not able to take in the fact that it was only in the act of supreme relinquishment that Christ's ministry was fulfilled.